One well-known method of treating large volumes of air is to move the air over heating coils so as to impart units of heat energy to the moving air. Such an arrangement is particularly useful when large internal areas are to be heated and where fresh outside air is to be used in the heating system. In such an arrangement the outside air is passed through a conditioning unit where a number of coil sets are contained, each set being internally heated so that as the fresh air passes heat units are transferred to the air thereby raising the temperature of the air.
As the ambient temperature of the outside or fresh air changes the amount of heat which must be transferred to the air in order to maintain a given final air temperature also changes. One method of accomplishing control of this heat in the past has been to control the incoming air so that a portion passes directly through and in face contact with the hot coils and a portion bypasses the coils, with the exact proportions depending on the ambient temperature and the desired final temperature. In the prior art, pivotaly mounted dampers have been used to accomplish such a proportioning of the air flow.
One problem with the pivotal arrangements is the large number of moving parts required to make all of the dampers move in synchronism with each other. Since the dampers are constructed with mating pairs of baffles around each coil set, it is necessary to move both portions of each baffle pair in opposite directions in order to achieve the desired selective proportioning. One example of such an arrangement is shown in U.S. Pat. No. 3,489,204 issued to A. Chaloka on Jan. 13, 1970. FIG. 3 of the Chaloka patent clearly shows the complex linkages required to accomplish the necessary movement. FIG. 3 of Chaloka also shows that each movable baffle must be pivotly mounted. Inherently, such a pivotal system is costly to construct, difficult to maintain and inefficient from the standpoint of the amount of energy required to move the baffles. In addition, since each damper comprises four distinct parts, each moving in a different direction with respect to each other, alignment problems are severe and tight air flow seals are difficult to obtain.
A still further problem exists when it is desired to pass air or fluid through different passages of a heat conditioning device; namely, the fact that each passage presents a different impedance to the flow of the fluid and thus the velocity of the fluid becomes a function of the passageway taken by that fluid. Such a result is troublesome in that the fluids passing through different passages will not mix properly thereby defeating the purpose of the selective proportioning device.
Accordingly, it is one object of our invention to arrange the proportioning dampers of an air of fluid treatment unit in a manner eliminating pivotal motion of the damper and in a manner which allows external adjustment of the dampers.
It is another object of our invention to reduce to a minimum the number of moving parts of each damper of an air or fluid treatment unit to a minimum.
And it is a still further object of our invention to provide selectively proportional openings in and around fluid heating coils where the relative velocities of the fluid passing through either opening are the same.